Speed Of Eye Movements Research Articles

Optimal integration of retinal and extra-retinal signals for heading perception

As we move forward in the environment we experience a radial expansion of retinal images, of which the center corresponds to the instantaneous direction of self-motion (heading). Humans and non-human primates can precisely perceive their heading directions even when they are making simultaneous pursuit eye movements, which shifted the center of the expansion pattern on retina. Previous controversial studies have shown that both retinal and extra-retinal strategy can account for accurate heading perception during pursuit. Here we propose that the visual system flexibly combine the retinal and the extra-retinal signals in a Bayesian-like statistically optimal fashion. To test predictions derived from this Bayesian-like framework, we devised a pair of experiments in which we independently manipulated the reliability of each input signals in a two alternative heading direction discrimination task. Two aspects of visual signal reliability were tested separately, the simulated heading speed and element motion coherency. Our results showed that the contribution of extra-retinal signals to heading judgments increased with increasing pursuit eye movement speed, and decreased with increasing simulated heading speed. Similarly, observers were relying on more of retinal signals instead of extra-retinal signals to support their heading judgments when we increased the coherency of element motion in retinal flow. We hope our findings can be helpful to unify previous differing observations in a rather sample framework. Meeting abstract presented at VSS 2014

Residency Training: The King-Devick test and sleep deprivation

The current study investigates the effect of sleep deprivation on the speed and accuracy of eye movements as measured by the King-Devick (K-D) test, a <1-minute test that involves rapid number naming. In this cohort study, neurology residents and staff from the University of Pennsylvania Health System underwent baseline followed by postcall K-D testing (n = 25); those not taking call (n = 10) also completed baseline and follow-up K-D testing. Differences in the times and errors between baseline and follow-up K-D scores were compared between the 2 groups. Residents taking call had less improvement from baseline K-D times when compared to participants not taking call (p < 0.0001, Wilcoxon rank sum test). For both groups, the change in K-D time from baseline was correlated to amount of sleep obtained (r(s) = -0.50, p = 0.002) and subjective evaluation of level of alertness (r(s) = 0.33, p = 0.05) but had no correlation to time since last caffeine consumption (r(s) = -0.13, p = 0.52). For those residents on their actual call night, the duration of sleep obtained did not correlate with change in K-D scores from baseline (r(s) = 0.13, p = 0.54). The K-D test is sensitive to the effects of sleep deprivation on cognitive functioning, including rapid eye movements, concentration, and language function. As with other measures of sleep deprivation, K-D performance demonstrated significant interindividual variability in vulnerability to sleep deprivation. Severe fatigue appears to reduce the degree of improvement typically observed in K-D testing.

Improvement of Reading Speed and Change of Eye Movements

Improvement of Reading Speed and Change of Eye Movements

Predictive smooth eye pursuit in a population of young men: I. Effects of age, IQ, oculomotor and cognitive tasks

Smooth eye pursuit is believed to involve the integration of an extraretinal signal formed by an internal representation of the moving target and a retinal signal using the visual feedback to evaluate performance. A variation of the smooth eye pursuit paradigm (in which the moving target is occluded for a short period of time and subjects are asked to continue tracking) designed to isolate the predictive processes that drive the extraretinal signal was performed by 1,187 young men. The latency to the onset of change in pursuit speed, the time of decelerating eye-movement speed and the steady state residual gain were measured for each subject and correlated with measures of other oculomotor (closed-loop smooth eye pursuit, saccade, antisaccade, active fixation) and cognitive tasks (measuring sustained attention and working memory). Deceleration time increased with increasing age, while education, general IQ and cognitive variables had no effect on predictive pursuit performance. Predictive pursuit indices were correlated to those of closed-loop pursuit and antisaccade performance, but these correlations were very weak except for a positive correlation of residual gain to saccade frequency in the fixation task with distracters. This correlation suggested that the maintenance of active fixation is negatively correlated with the ability to maintain predictive pursuit speed. In conclusion, this study presents predictive pursuit performance in a large sample of apparently healthy individuals. Surprisingly, predictive pursuit was weakly if at all related to closed-loop pursuit or other oculomotor and cognitive tasks, supporting the usefulness of this phenotype in the study of frontal lobe integrity in normal and patient populations.

Eye Movement during Facial Affect Recognition by Patients with Schizophrenia, Using Japanese Pictures of Facial Affect

A possible relationship between recognition of facial affect and aberrant eye movement was examined in patients with schizophrenia. A Japanese version of standard pictures of facial affect was prepared. These pictures of basic emotions (surprise, anger, happiness, disgust, fear, sadness) were shown to 19 schizophrenic patients and 20 healthy controls who identified emotions while their eye movements were measured. The proportion of correct identifications of 'disgust' was significantly lower for schizophrenic patients, their eye fixation time was significantly longer for all pictures of facial affect, and their eye movement speed was slower for some facial affects (surprise, fear, and sadness). One index, eye fixation time for "happiness," showed a significant difference between the high- and low-dosage antipsychotic drug groups. Some expected facial affect recognition disorder was seen in schizophrenic patients responding to the Japanese version of affect pictures, but there was no correlation between facial affect recognition disorder and aberrant eye movement.

Visual-manual tracking and vestibular function during a seven-day dry immersion

The seven-day DI experiment provided an opportunity to study the effects of decreased proprioceptive, tactile and support afferentation on the vestibular function and visual-manual tracking. Before and after immersion, six subjects participated in videooculographic evaluation of the static torsion otolith-cervicoocular reflex (OCOR) in response to head inclination at 30 degrees in the frontal plane and dynamic vestibular-cervicoocular reactions to head longitudinal rotations at 0.125 Hz. In addition, the hand-eye motor coordination of tracking a jerky (sinusoidal) or smooth (linear) movement of point targets along the horizontal or the vertical was evaluated based on the data of electrooculography and records of manipulations with the joystick during immersion. The computerized test was performed in virtual spectacles dsplaying images of visual stimuli and hand motor acts. Computed parameters included latent reaction time, amplitude, speed and time of eye and hand movements, and gains of optooculomotor reactions and manual tracking as a ratio of eye/hand to visual stimulus speed. Testing was fulfilled before the experiment, in 3 hrs. of immersion, on days 3 and 6 of staying in the bath, in the initial hours after immersion, and on day 3 of recovery. It was shown that removal of support and minimization of proprioceptive afferentation had a profound effect on the ocular tracking rather than hand pursuance of visual stimulus. Accuracy of manual tracking was better comparing with the eye tracking in all the subjects. This was the first time when we observed changes in the peripheral vestibular system in two out of 6 subjects, i.e. inversion of static torsion OCOR and positional nystagmus on the background of converted reflex which did not mar the parameters of oculo-manual tracking.

Testing a postselectional account of across-dimension switch costs

In visual search for a pop-out target, responses are faster when the target dimension from the previous trial is repeated than when it changes. Currently, it is unclear whether these across-dimension switch costs originate from processes that guide attention to the target or from later processes (e.g., target identification or response selection). The present study tested two critical predictions of a response-selection account of across-dimension switch costs-namely, (1) that switch costs should occur even when visual attention is guided by a completely different feature and (2) that changing the target dimension should affect the speed of responding, but not the speed of eye movements to the target. The results supported both predictions, indicating that changes of the target dimension do not affect early processes that guide attention to the target but, rather, affect later processes, which commence after the target has been selected.

Noise Correlations in Cortical Area MT and Their Potential Impact on Trial-by-Trial Variation in the Direction and Speed of Smooth-Pursuit Eye Movements

Smooth-pursuit eye movements are variable, even when the same tracking target motion is repeated many times. We asked whether variation in pursuit could arise from noise in the response of visual motion neurons in the middle temporal visual area (MT). In physiological experiments, we evaluated the mean, variance, and trial-by-trial correlation in the spike counts of pairs of simultaneously recorded MT neurons. The correlations between responses of pairs of MT neurons are highly significant and are stronger when the two neurons in a pair have similar preferred speeds, directions, or receptive field locations. Spike count correlation persists when the same exact stimulus form is repeatedly presented. Spike count correlations increase as the analysis window increases because of correlations in the responses of individual neurons across time. Spike count correlations are highest at speeds below the preferred speeds of the neuron pair and increase as the contrast of a square-wave grating is decreased. In computational analyses, we evaluated whether the correlations and variation across the population response in MT could drive the observed behavioral variation in pursuit direction and speed. We created model population responses that mimicked the mean and variance of MT neural responses as well as the observed structure and amplitude of noise correlations between pairs of neurons. A vector-averaging decoding computation revealed that the observed variation in pursuit could arise from the MT population response, without postulating other sources of motor variation.

Relationship Between Adapted Neural Population Responses in MT and Motion Adaptation in Speed and Direction of Smooth-Pursuit Eye Movements

We have asked how sensory adaptation is represented in the response of a population of visual motion neurons and whether the neural adaptation could drive behavioral adaptation. Our approach was to evaluate the effects of about 10 s of motion adaptation on both smooth-pursuit eye movements and the responses of neuron populations in extrastriate middle temporal visual area (MT) in awake monkeys. Stimuli for neural recordings consisted of patches of 100% correlated dot textures. There was a wide range of effects across neurons, but on average adaptation reduced the amplitude and width of the direction tuning curves of MT neurons, without large changes in the preferred direction. The effects were greatest when the direction of the adapting stimulus corresponded to the preferred direction of the MT neuron under study. Adaptation also reduced the amplitude of speed-tuning curves, again with the greatest effect when the adapting speed was equal to the preferred speed. The adapted tuning curves were shifted toward lower preferred speeds as the adapting speed increased. We constructed populations of model MT neurons based on our experimental sample and showed that the effects of adaptation on the direction and speed of pursuit eye movements were predicted when a variant of vector averaging decoded the responses of a subset of the neural population. We conclude that the effects of motion adaptation on the responses of MT neurons can support behavioral adaptation in pursuit eye movements.

Speed and accuracy of saccades, vergence and combined eye movements in subjects with strabismus before and after eye surgery

The purpose of the study was to examine spatio-temporal characteristics of horizontal eye movements in the natural space (saccade, vergence and combined movements) in young subjects with early onset convergent or divergent strabismus. Nine young subjects (8–20 years old) were tested: three with divergent strabismus, six with convergent strabismus. A standard paradigm was used to elicit pure horizontal saccades at far and at close viewing distance, pure vergence along the median plane (convergence and divergence) and saccades combined with vergence movements. Horizontal eye movements from both eyes were recorded by a photoelectric device. Eye movements were recorded before surgery, and, for the majority of the subjects, two times after surgery. Before surgery the accuracy of convergence and divergence movements in their pure or combined form was poor with respect to normal values. The mean velocity of convergence was also abnormally slow. Strabismus surgery improved significantly the accuracy of these types of eye movements. The speed of pure convergence and of divergence combined movements increased significantly after surgery. We concluded that poor vergence eye movement’s performance, particularly those found for convergence in strabismic subjects could be due to impairment in the central structures related to sensory disparity inputs. Adaptive mechanisms promoted by the realignment of the eyes could be at the origin of the improvement in the vergence performances observed in our subjects after strabismus eye surgery.

Normal Speed and Accuracy of Saccade and Vergence Eye Movements in Dyslexic Reader Children

Objective. Latency of eye movements depends on cortical structures while speed of execution and accuracy depends mostly on subcortical brainstem structures. Prior studies reported in dyslexic reader children abnormalities of latencies of saccades (isolated and combined with vergence); such abnormalities were attributed to deficits of fixation control and of visual attention. In this study we examine speed and accuracy characteristics of horizontal eye movements in natural space (saccades, vergence and combined movements) in dyslexic reader children. Methods. Two paradigms are tested: gap paradigm (fixation offset 200 ms prior to target onset), producing shorter latencies, in both non-dyslexic reader and dyslexic reader children and simultaneous paradigm. Seventeen dyslexic reader children (mean age: 12 ± 0.08 years) and thirteen non-dyslexic reader children (mean age: 12 ± 1 years) were tested. Horizontal eye movements from both eyes were recorded simultaneously by a photoelectric device (Oculometer, Dr. Bouis). Results. For all movements tested (saccades, vergence, isolated or combined) and for both paradigms, the mean velocity and accuracy were similar in dyslexic readers and non-dyslexic readers; no significant difference was found. Conclusion. This negative but important result, suggests no dysfunction of brainstem ocular motor circuits in dyslexic readers. It contrasts results on latencies related to visual attention dysfunction at cortical level.

イタリアンサイプレスの対植による幾何学式庭園に対する眼球運動の変化に関する研究

The effects of pair planting of Italian Cypress on the visual characteristics of geometric garden are discussed with the analysis of eye movements of 16 subjects. The distribution of eye fixation and eye movement speed inspecting French Garden from its east end are compared before and after the planting of pair trees which locate symmetrically at the western extension of east and west axe of the garden. The center of eye point distribution tends to concentrate on the central area including flower base after the planting of pair tree. And, the number of eye movement in the upper part of central area significantly increased in the male subjects. Contrarily, the number of eye movement in the lower part of central area significantly increased in the female subjects. Therefore, the characteristics of eye movement mentioned above are considered to indicate that the pair planting has a visual effect to conceive the axe of geometric garden.

Effects Of Sports Vision Training On Visual Skill Performance

The primary sensory input in sport is through the vision system. Recently, many elite athletes have begun sports vision training in an effort to enhance visual skills to ultimately improve athletic performance. There is, however, limited research examining the effect of vision training on visual and athletic performance. PURPOSE: To evaluate the effects of sports vision training on visual performance. METHODS: This study is a retrospective effort to evaluate existing sports vision data from a ten year period collected as part of the United State Air Force Academy's sports vision training program. 1,118 athletes (905 males, 213 females), all intercollegiate athletes of various sports that rely heavily on visual inputs, participated in a sports vision training program. To track athlete progress, skills such as eye movements, accommodation, vergence and eye-hand speed and accuracy of movements were tested before and after a series of training sessions. Athletes trained for approximately 20 minutes per session, 2 to 3 times per week, for up to four years. RESULTS: Performance on each visual skill improved significantly (p < 0.05) as a result of the training. The increase in visual performance occurred in a step wise fashion meaning the more the athlete trained, the better their performance. After 31 + training sessions, eye movement speed increased up to 24%, vergence up to 55%, accommodation up to 36%, and eye-hand speed and accuracy up to 150%. CONCLUSION: Sports vision training can improve an athlete's visual system skills. The next step in this line of research is to evaluate the effects of visual skill improvement on actual athletic performance. Disclaimer: The views expressed in this article are those of the authors and do not reflect the official policy or position of the United States Air Force, the Department of Defense, or the US Government.

Scanpaths in reading and picture viewing: Computer-assisted optimization of display conditions

A review of the literature shows that in reading and picture viewing cognitive skills play a key role along with visual acuity. Optimal processing conditions are reached only with letter and object sizes that match both cognitive skills and visual acuity. Beginning readers with normal vision need larger letters than skilled readers. In reading, eye movements step the fovea, a high-acuity region 2 ∘ diameter, at the physiological pace of the visual system about 4 times per second. A simple computer-based procedure is described that determines the best acuity- and skill-matched letter (or object) sizes in the context of an optimal reading eye movement speed of 8 deg/s.

Eye movement and driving behaviour in curved section passages of an urban motorway

This study focuses on driver eye movements and vehicle control behaviour, factors implicated in the human errors that are considered to be important factors that may cause traffic accidents. Some curved sections of urban motorways have a comparatively high frequency of accident occurrence. The authors attempted to link three factors, namely eye movement, roadway alignment, and driver speed and steering control. In order to analyse the factors that lead to human error, an in-car experiment was carried out on some routes with curved sections of the Tokyo Metropolitan Expressway. This study focuses on single-car collisions occurring primarily in free-flow regions. Using the results of the experiment, the authors were able to analyse the factors that produce human error in relation to motorway alignment, eye movement, and centrifugal acceleration in the curved sections. As a result, the authors proposed a model that evaluates the risk of curved sections in relation to the driver's eye movement and driving behaviour.

The Influence of Brightness Highlighting on Eye Movements within a Cockpit Display of Traffic Information

Several experiments were conducted to examine the effect of brightness highlighting on search of a target aircraft among distractor aircraft within a cockpit display of traffic information (CDTI). The present experiment partially replicated the design of one of these experiments, adding an examination of eye movements. The display presented homogenous all bright, all dim, or mixed bright and dim aircraft. Within the mixed display, target aircraft were non-predictive and either bright or dim. Results showed that with the mixed display, participants yielded slower detection times, exhibited more eye fixations, and searched with longer paths, compared to the homogenous all bright or dim displays. The duration of the fixation and the speed of eye movements did not show any difference between the homogeneous and mixed displays. The present detection time analysis did not replicate previous experimental results and this is likely due to the fewer trials given in the current experiment. The present results demonstrated how using highlighting to segregate information domains may impose costs on visual search performance in the early stages of a search task.

Divergence eye movements are dependent on initial stimulus position

Previous studies on the speed and latency of convergence and divergence eye movements have produced varied, sometimes contradictory, results. Four subjects were studied and tracked 4° disparity step changes for convergence and divergence at different initial target positions. Here we report that the dynamics of divergence movements not only differ from convergence movement, but depend on the initial vergence position. Velocities of divergence eye movements in response to targets that were initially near to the subject were approximately twice that of responses to initially distant targets and also exhibited shorter temporal properties. Hence, while convergence responses are fairly similar irrespective of the initial position, divergence dynamic and temporal properties are dependent on the initial stimulus position. It is speculated that the differences observed in divergence may be the result of nonlinear properties of the extraocular muscles or a difference in the underlying neural controller potentially a difference in the magnitude of the fusion initiating component of divergence.

A population decoding framework for motion aftereffects on smooth pursuit eye movements.

Both perceptual and motor systems must decode visual information from the distributed activity of large populations of cortical neurons. We have sought a common framework for understanding decoding strategies for visually guided movement and perception by asking whether the strong motion aftereffects seen in the perceptual domain lead to similar expressions in motor output. We found that motion adaptation indeed has strong sequelae in the direction and speed of smooth pursuit eye movements. After adaptation with a stimulus that moves in a given direction for 7 sec, the direction of pursuit is repelled from the direction of pursuit targets that move within 90 degrees of the adapting direction. The speed of pursuit decreases for targets that move at the direction and speed of the adapting stimulus and is repelled from the adapting speed in the sense that the decrease either becomes greater or smaller (eventually turning to an increase) when tracking targets move slower or faster than the adapting speed. The effects of adaptation are spatially specific and fixed to the retinal location of the adapting stimulus. The magnitude of adaptation of pursuit speed and direction is uncorrelated, suggesting that the two parameters are decoded independently. Computer simulation of motion adaptation in the middle temporal visual area (MT) shows that vector-averaging decoding of the population response in MT can account for the effects of adaptation on the direction of pursuit. Our results suggest a unified framework for thinking, in terms of population decoding, about motion adaptation for both perception and action.

Measurement of information processing load and visual load on a dynamic information processing task

A dynamic visual information processing task was designed to investigate time-based and intensity-based factors on an operator's information processing load as measured by reaction time, pupil diameter, and eye movement parameters. The time-based factor was manipulated by the target rate and scanning rate while the intensity-based factor was manipulated by the difference between a simple reaction task and a physical matching (choice reaction) task. Nine participants tracked the scanning line at two different scanning rates and were required to respond to two designated targets presented singly at two different temporal frequencies. The results indicated that task difficulty (the intensity-based factor) had a significant effect on the reaction time. Target rate and scanning rate were integrated as one time-based factor in terms of three sweeping angles. The time-based factor was found to have a significant effect on the fixation time, saccade amplitude, fixation frequency, eye movement speed, reaction time and hit rate. No interaction effect was found between time-based and intensity-based factors. The time pressure (defined by the time required divided by the time available) based on a model human processor was positively related to scanning rate, target rate and task difficulty. It was found to be the most objective and reliable if time required can be reliably predicted based on a predictive model approach.

Eye movements in the visual search of word lists

The word identification span refers to the area of the visual field in which words can be identified during a single fixation. The purpose of the study was to estimate the vertical word identification span in a visual word search task, in which words were arranged in a vertical list. In addition, we studied the effect of list layout (orientation, length, and line spacing) on the speed of search and eye movements. The task of the observer was to identify a target word in a word list, where the other words were distracters. Threshold search time, that is, stimulus presentation time for correct identification at a probability level of 0.79, was determined by using a multiple alternative staircase method. Eye movements were recorded simultaneously. The results showed that, in vertical lists, 4–5 words could be identified during a single fixation. Thus, the vertical word identification span was 4–5 character spaces, whereas according to previous studies the horizontal word identification span is about 10 character spaces, which corresponds to 1–2 words. There were fewer fixations and the saccade amplitudes were smaller for vertical than for horizontal lists of the same length. However, search times did not depend on list orientation. This was due to longer fixation times for vertical lists. Further, since average fixation duration for vertical lists was longer than for horizontal lists, processing time seems to depend on the number of items within the span.